E-cigarettes are increasingly used by teenagers, who are particularly vulnerable to the addictive properties of nicotine. With the exclusion of menthol, the use of flavor additives has been banned from traditional cigarettes, while e-cigarettes (e-cigs) are marketed in over 7,000 different flavors. We hypothesize that flavorants enhance nicotine reward through sensory and/or natural reward mechanisms. As a consequence, flavored e-cigs may promote nicotine experimentation, dependence, and eventually, the use of regular cigarettes. Despite the fact that the FDA has recently regulated the sales of flavored e-cigs to minors, no flavor ban has been implemented, and adolescents could still obtain flavored e-cig products through friends or unscrupulous sellers. Furthermore, understanding how flavors influence e-cig use is important for the implementation of regulatory rules that can reduce potential disease and death deriving from the consumption of this increasingly popular tobacco product. The overall goal of this application is to compare the rewarding and reinforcing properties of flavored vs. non-flavored e-cigs in adolescent and adult mice, and identify the neural substrates responsible for the enhancing effects of flavorants. Our hypothesis is that flavored e-cigs are more rewarding than non-flavored e-cigs and that flavor additives promote and sustain nicotine seeking in adolescents due to the combined influence of flavorants and nicotine on the ventral striatum. The first goal is to determine whether flavorants enhance adolescent nicotine reward and promote nicotine self- administration, and compare their effects in adult mice. The second goal is to understand how e-cig flavorants are encoded in the ventral striatum during acquisition of e-cigarette vapor preference and self-administration. The third goal is to determine whether exposure to e-cig flavorants alters synaptic plasticity in the ventral striatum and whether it modifies cellular responses to nicotine. Our experiments will combine behavioral approaches with tetrode recordings during behavior and brain slice electrophysiology to determine how e-cigarette nicotine vapor affects reward-associated brain areas, and whether flavorants (e.g. fruit or mint) have additive or synergistic effects.